Triallyl Isocyanurate Enabling Robust Interfacial Barrier with Exceptional High‐Temperature Resilience for Ni _0.9 Co _0.06 Mn _0.04 ||Si@C Batteries

Severe interfacial instability between the nickel‐rich layered oxide cathode and the silicon‐based anode at high temperatures leads to rapid decay of electrochemical performance. Herein, triallyl isocyanurate (TAIC) is investigated as a simple and highly effective multifunctional electrolyte additive, which dramatically enhances the high‐temperature performance of LiNi _0.9 Co _0.06 Mn _0.04 O ₂ (Ni90)||Si@C full cells. The TAIC preferentially polymerized to form a homogeneous cathode electrolyte interphase and solid electrolyte interphase. This fundamentally inhibits successive electrolyte decomposition and accommodates the volume changes of silicon anode. Meanwhile, the triazine‐ring nitrogen atoms may chelate transition metal ions (Ni ²⁺ , Co ²⁺ ) dissolved from the cathode, preventing their migration to and catalytic degradation of the anode. This two‐pronged strategy fundamentally inhibits derivative side reactions at the electrode/electrolyte interface. As a result, incorporating only 1.0 wt% TAIC into a conventional carbonate‐based electrolyte enables the cell to retain 86.1% of its initial capacity after 150 cycles at 45°C, starkly contrasting the 78.7% retention of the baseline cell. The TAIC‐modified cell exhibits negligible swelling and superior capacity retention (from 13.94% to 91.58%) and recovery (from 55.97% to 92.46%) after high‐temperature storage. This work proposes a novel and industrially viable electrolyte engineering strategy, breaking the vicious cycle of interfacial degradation in high‐energy lithium‐ion batteries under thermal stress.